One challenge to understanding and preventing malaria is that people who are infected with Plasmodium parasites, and potentially infectious to mosquito vectors, are frequently asymptomatic, hence not recognized as contributing to transmission dynamics. This research project will determine which people are infected with Plasmodium gametocytes, evaluate resulting mosquito infections that derive from those infectious people, and infer population-level patterns of malaria risk that emerge from these transmission events. We will take advantage of ongoing NIH-funded research (International Centers of Excellence for Malaria Research) in southern Malawi where different intensities of transmission occur. Using a new molecular-genetic detection technique (qRT-PCR) for recognizing low-density P. falciparum gametocytes that are not normally seen through microscopy, we will explore associations between infection and symptoms, treatment, age and various environmental/behavioral risk factors. Specifically, we will test three hypotheses addressing 1) the prevalence of parasitemia, and specifically gametocytemia, in relation to transmission intensity and treatment, 2) patterns of gametocytemia with regard to age, mosquito ecology, and anti-malarial interventions, and 3) impacts on household-level transmission to Anopheles vectors. This project is innovative in using a new molecular diagnostic method to evaluate naturally-infected, asymptomatic people combined with non-experimental field transmission to mosquitoes found in common living contexts of the region. We expect our results to have household- and community-level transmission implications for treatment and prevention that may affect the seasonality and annual re-intensification of transmission in ways that are dynamically counterintuitive.